Refining vegetable oils



United States Patent VEGETABLE nus Lester P. Hayes and Hans Wolff, Decatur, Ill., assignors 'to A. E. Staley Manufacturing Company, Decatur, 111.,

a corporation of Delaware No D w n A ti J ua as. 5.

Serial No. 333,374

20 Claims. (Cl. 260-424) This invention relates, broadly, to innovations and improvements in the refining of vegetable oils. More particularly, the invention pertains to the use of certain acid anhydrides-as degumming agents for lecithin-bearing vegetable oils such as soybean oil, cottonseed oil, perilla oil, linseed oil, peanut oil, corn oil and tung oil whereby such oils can be rendered both heat break-free and acid break-free. The break-free vegetable oils provided by this invention are suitable for edible and industrial purposes requiring vegetable oils of the highest quality.

Crude vegetable oils of the class referred to above contain substances which in contact with water tend to settle out or seperate from the main body of the oil. Such substances are commonly referred to and designated as gum or gums and they are obtained in the commercial refining of vegeable oils, such as crude soybean oil, by the addition of water to the crude oil followed by centrifuging the mixture to separate the water component containing the gums from the main body of the oil. These gums, after drying, and in certain instances after additional treatment, are marketed commercially as lecithin.

The separation of the gums or lecithins is carried out not only because of the commercial value .of these substances as by-products but also because, their presence in the oil is undesirable for most of the ultimate uses made of the oils. However, the water degurnming treatment normally does not remove the final traces of lecithin or other gumforming substances. Consequently, the residual amounts of these substances remaining in the oil, even though small, are suficient to cause a darkening and clouding of the oils on heating, usually with the formation of a visible black flock. This heck is com,- monly known as break in the art and an oil which Shows h a l lat n q d ken n 9 he in s sidered to contain break.

If an oil on heating to 550 F. shows no darkening or flock but on the contrary tends to get lighter, i. e. heat bleaches, such an oil is considered to be heat break-free oil or a non-break oil. In addition, if the oil on heating to 550 'F. in the presence of hydrochloric acid shows no darkening or flock but lightensin color, it is considered to .be an acid break-free or Gardner breakfree oil according to American Oil Chemists Society, Ofi'icial Method Ca -40, May, 1949.

The so-called break in industrial oils is undesirable because it interferes with various processing operations and shows up adversely in finished products. For example, large quantities of soybean oil are used by the paint and varnish industry, one of the principal uses therein being in the preparation of alkyd resins. These resins are used extensively in making white enamels (e. g. refrigerator enamels) and other high grade industrial finishes and any break in the oil tends to darken and detract from the white color of such finishes.

Break is also undesirable when degumrned vegetable oils are used for making edible oils since the production of edible vegetable oils usually involves a deodorization 2,782,216 e ed. reels, 195? s p w ei the oi ar he d in t e pr n e of stea to temperatures of 350500 F. at pressures substantially below atmospheric. If there is break in the oils when they are deodorized in such a manner, they turn dark and their flavor is adversely afiected. I

Heretofore, the most extensively used techniquefor obtaining break-free vegetable oils has been the so-called alkali-refining process.- Essentially this pro cessconsists of washing either the crude oil or the water degummed oil with aqueous caustic solution. The by-product of this alkali-refining operation is referred to as soapstock and is a dark greasy substance consisting mainly a mu: ture of soaps, neutral oil and water. The alkali-refining technique entails loss of valuable neutral .oilfpartly by entrainment of the neutral ,oil in thesoapstock and partly by hydrolysis of the neutral oil. i

In addition to the alkali-refining technique, a number of other methods have been proposed for obtaining break-1 free oils but insofar as has been learned such methods have not been adopted in the industry. PatienfNo. 2,410,926 dated November 12, 1946, for example, mentions sulfamic, oxalic, citric, picric and'maleic acids as being useful degumming agents for obtaining breakdree oils. Patent No. 2,448,434 dated August 31, 19,148 discloses the use of halogenated low aliphatic acids as degumming agents for use in preparing break-free vegetable oils. None of the degumming agents disclosed in these patents has proven to be commercialy successful for one reason or another.

It ha b n nd ac d n 9 t e r sen inven i n the h us of c t i a i an one a he pr e pr.

wat -drumm n s etsb cbi 'n nit t e econ mi production of br'ealefree vegetable oils and oflfers pneuest a v n a e e e h m h d u te is hea ibr art for obtaining break free oils. Acid anhydrid es of lower alkyl aliphatic monobasic and dibasic acids may be used as degumming agents with water according to' this invention. Such acid anhydrides have one o f the two following general structural formulas, depending on whether the anhydride is derived from a 'monobasic" or "a dibasic acid. r

The present invention offers the following advantages and improvements over the alkali-refiningof vegetable oils, which heretofore has been the process mos t'ex tensively used for obtaining break-free oils:

' (l) The break-free oils may now be obtained in the deguinming operation alone and no additional refining step is required, whereas alkali refining involves an added step over and above the degumming treatment.

l (2) Fatty acids can now be recovered in a single step as once-distilled fatty acids during the .deodorization operation. These fatty acids are "much .more valuable than the soa'pstock obtained in the alkali-refining technique from which pure fatty acids can be recovered only in a two-step separation, i. .e. acidification and distillation.

-(3) The gloss of .neutral oil is substantially reduced because of ,the elimination of the separate alkali-refining more efliciently from crude vegetable oils which have not been either partially refined or allowed to stand long enough to permit a portion of the gums to settle out. In fact, the process of the present invention works better when used to refine raw crude oils which have not been allowed to stand or settle or refined in any way.

While vegetable oils broadly may be treated in accordance with the present invention, especially lecithin hearing vegetable oils, it has particular utility in connection with the treatment of soybean oil since soy lecithin is the most important commercial lecithin. In addition to soybean oil, other oils which may be treated to advantage in accordance with the present invention are corn oil, cottonseed oil, peanut oil, linseed oil, perilla oil and tung oil.

An important object of the invention is an economical method of obtaining heat break-free and acid break-free vegetable oils, particularly soyabean oil, without the use of an alkali, by treating the crude oil in a water-degumming operation with a small quantity of an acid anhydride of a lower alkyl aliphatic monobasic or dibasic acid such as acetic, propionic, butyric, maleic or succinic acid anhydride. Mixed acid anhydrides or lower alkyl substituted acid anhydrides of this class may also be employed such as, for example, mixed acetic, propionic acid anhydride, monomethyl succinic acid anhydride, and dimethyl succinic acid anhydride.

Another object of the invention is a method of obtaining heat and acid break-free vegetable oils, particularly soybean oil, without the formation ofv soapstock, with little or no loss of neutral oil which comprises incorporating in the water degumming step a small amount of acid anhydride of the class referred to above, agitating the admixture of water, oil and anhydride for a suitable period at an elevated temperature and then centrifuging the mixture to separate the aqueous phase, the resulting degummed oil being heat and acid-break-free and of a quality useful for making edible oils of superior flavor properties and for formulating white baked-on enamel finishes and for other industrial uses.

Another object of the invention is an economical onestep method of degumming lecithin-bearing vegetable oils to render the same both heat and acid break-free.

Another object of the invention is a method of degumming lecithin-bearing vegetable oils to render the same both heat and acid break-free which is especially efficient in connection with oils which have not been partially degummed as the result of standing or partial refining.

Still another object of the invention is an economical process of making heat and acid break-free vegetable oils wherein fatty acids can be recovered during deodorization of the break-free oils as once-distilled free fatty acids.

Other objects of the invention will, in part, be obvious, and will, in part, appear hereinafter.

The process of the present invention involves incorporating a minor amount of a suitable acid anhydride in the aqueous degumming treatment given a vegetable oil. The anhydride may be added either (1) to the degumming water, (2) to the oil, or (3) to the oil-degumming water mixture. In the treatment of crude soybean oil according to the invention, the anhydride may be added within the range of 0.05-1% on the basis of the weight of the oil with a preferred range being from 0.080.2%. The treatment may be carried out at a temperature within the range of 40-100" 0, and the preferred temperature range is from 6085 C. The duration of the treatment is not particularly critical but should normally be kept as short as practical in the interest of economy.

Other vegetable oils can be treated according to the same general procedure and the operating ranges and conditions suitable for treating soybean oil are, in general, also suitable for treating the other vegetable oils.

The following specific examples will serve further to indicate the nature and scope of the invention and inform those skilled in the art as to various procedures which may be employed to practice the invention and also sug gest others coming within the scope of the invention.

EXAMPLE 1 1500 grams of crude extracted soybean oil (i. e. oil obtained by the solvent extraction process) having 0.5% break according to the A. O. C. S. Otficial Method Ca 10-40 were warmed to a temperature of C. 1.5 grams of acetic anhydride were added to the oil with stirring. After five minutes 22.5 grams of water were added and the mixture was stirred for 15 minutes during which time the temperature was raised to C. The mixture was then introduced into a batch type centrifuge and was centrifuged for 15 minutes at 1800 R. P. M. to separate the aqueous component containing the gums from the oil. The resulting oil was break-free according to the heat and Gardner break test. The oil bleached during the Gardner test. The oil was bleached in the usual manner with bleaching clays and active carbon and then deodorized in known manner with steam at a temperature of 225 C. at a pressure of 4 millimeters of mercury. Prior to deodorization the free fatty acid content (F.F.A.) of the oil was 0.27%. After deodorization it was 0.008%. 2.5 grams of fatty acids were recovered in the condenser.

The oil that was obtained was first quality edible oil and rated somewhat higher in flavor tests than edible soybean oil obtained by alkali refining the water-degummed crude oil followed by deodorization. The lecithin obtained on drying the gums was slightly more fluid than the lecithin ordinarily obtained from soybean oil by the water degumming process.

EXAMPLE 2 This was an example to determine whether or not the acetic anhydride used in Example 1 was merely the chemical equivalent in the process of the corresponding acid, i. e. acetic acid. Accordingly, the process of Example 1 was repeated but the 1.5 grams of acetic anhydride were replaced with 3 grams of acetic acid. The quantity of acetic acid which is equivalent to the amount of anhydride used in Example 1 would have been 2.55 grams, and therefore the 3 grams were in excess of the amount that would theoretically be required. The experiment was unsuccessful in that the acetic acid gave a partially degummed oil which was cloudy and exhibited no heat bleaching on the Gardner test. The process was repeated using 2.55 grams of acetic acid with substantially the same results. Accordingly, it was apparent that the anhydride plays some unique role in the refining process and it does not perform merely as one form of the corresponding acid.

EXAMPLE 3 The process of Example 1 was repeated but crude soybean oil obtained from the expeller process was used in place of the extracted soybean oil. The resulting centrifuged oil was bright and heat bleached well. It was break-free. The oil after bleaching and deodorizing was comparable in quality to the finished oil obtained in the process of Example 1.

EXAMPLE 4 EXAMPLE 22.5 grams of water were added to 1500 grams of crude extracted soybean oil at 60 C. After the mixture was stirred for five minutes, 1.5 grams of acetic anhydride was added and the stirring continued for 20 minutes. The mixtures was then centrifuged but the resulting oil was not quite break-free by the Gardner test.

EXAMPLE 6 I The process of Example 5 was repeated but the amount of acetic anhydride was increased 2 grams. T he resulting oil was break-free by the Gardner test and was bleached and deodorized to yield an edible soybean oil of first quality.

EXAMPLE 7 The process of Example 1 was duplicated except that all of the deg'umrning steps of the process were carried out at a temperature of 40 C. After centrifuging, the oil obtained was break-free by the Gardner test and was bleached and deodorized to provide an edible oil of first grade quality.

EXAMPLE 9 The process of Example 1 was duplicated except that all of the degumming steps of the process were carried out at 75 C. After centrifuging, the oil obtained was break-free by the Gardner test and it was bleached and deodorized to yield an edible soybean oil of first grade quality.

EXAMPLE 10 The process of Example 1 was duplicated except that all of the degumming steps were carried out at a temperature of 95 C. After centrifuging, the oil was breakfree by the Gardner test and it was bleached and deodorized to provide an edible oil of. first grade quality.

EXAMPLE 1 1 This example was the same as Example 1 except that the crude soybean oil of Example 1 was replaced with crude extracted soybean oil having 0.31% Gardner break. The oil obtained after centrifuging was break-free by the Gardner test and it was bleached and deodorized to provide an edible oil of first grade quality.

EXAMPLE 12 This example was the same as Example 1 except that 1500 grams of crude extracted soybean oil was used which contained 0.21% Gardner break. After centrifuging, the oil obtained was not break-free by the Gardner test but was cloudy.

EXAMPLE 13 Example 12 was repeated using 3.0 grams of acetic anhydride. After centrifuging, the oil was break-free by the Gardner test and was bleached and deodorized to yield a first grade quality edible soybean oil.

EXAMPLE 14 To 1500 grams of crude extracted soybean oil warmed to '60 C. were added 1.5 grams of powdered succinic anhydride with stirring. After 15 minutes, 22.5 grams of water were added and stirring continued as the temperature was raised to 80 C. The stirring was continued for--rninutes--and then the mixture was centrifuged to separate out the gums. The resulting oil was break-free by the Gardner test and was bleached and deodorized to yield an edible soybean oil of first grade quality.

EXAMPLE 15 The process of Example 14 was repeated using only 0.75 grams of powdered succinic anhydride. The oil obtained upon centrifuging was break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 16 This example was the same as Example 14 except that the water was added before the succinic anhydride. The oil obtained upon centrifuging was break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 17 The same as Example 14 except that 1.5 grams of maleic anhydride were used instead of the succinic anhydride. The oil obtained upon centrifuging was break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 18 This example was the same as Examplel but 1.5 grams of propionic anhydride were used in place of the acetic anhydride. The centrifuged oil was break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 19 This example was the same as Example 1 but 1.5 grams of butyric anhydride were used in place of the acetic anhydride of Example 1. The centrifuged oil was break-free according to the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 20 To 1500 grams of crude extracted soybean oil a solution of 3.2 grams of maleic anhydride in 20 cc. of water was added and the mixture was stirred for 15 minutes at a temperature of C. The mixture was then centrifuged and a break-free oil was obtained according to the Gardner test which was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 21 This example was the same as Example 20 except that the maleic' anhydride of Example 20 was replaced with 3.2 grams of succinic anhydride. The centrifuged oil was break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 22 This example was the same as Example 20 except that the maleic anhydride was replaced with 3.2 grams of propionic anhydride. The centrifuged oil obtained was heat break-free by the Gardner test and was bleached and deodorized to yield an edible oil of first grade quality.

EXAMPLE 23 To 400 grams of raw crude linseed oil there was added 0.4 gram of acetic anhydride with stirring. After five minutes 2 grams of water were added and the-mixture stirred at 60 C. for 15 minutes. The mixture wasthen centrifuged after first being allowed to cool to 40 C. The oil obtained was break-free linseed oil by the Gardner test.

EXAMPLE 24 This example was the same as Example 23 except that maleic anhydride was used in place of the acetic anhy dride; The linseed oil obtained bycentrifuging was breakfree by the Gardner 'tes't;

. EXAMPLE To 1000 grams of crude expeller corn oil was added 1 gram of 'acetic anhydride. The temperature of the mixture was raised to 70 C. and grams of water were added with stirring. After minutes at C. the mixture was centrifuged and a bright oil was obtained which was break-free by the Gardner test.

EXAMPLE 26 This example was the same as Example 25 except that 1000 grams of crude cottonseed oil were used in place of the corn oil. The resulting centrifuged cottonseed oil was break-free by the Gardner test.

EXAMPLE 27 This example was the same as Example 25 except that 1000 grams of crude peanut oil were used in place of the corn oil. Again the centrifuged oil was break-free by the Gardner test.

The process of the present invention may be carried out in known type equipment, either as a batch process or as continuous process.

In addition to the foregoing examples, a large number oil, and acetic anhydride was the acid anhydride used because this is preferred at the present time due to its relative cheapness and ready availability, ease of removal from the oil and the fact that it gives results which are as satisfactory as those obtained with other acid anhydrides of the class that can be used.

Soybean oils containing various percentages of break were used in the experiments that were made to determine the various operating factors and other variables. S0- called full crude extracted soya oil, which is the soy bean oil as it comes from the solvent extraction process, has a break content ranging from about 0.48% to 0.70% depending upon the beans used and such factors as the locality in which the beans are raised, the type of the beans, and the age of the beans, etc. In order to determine variations in the process which were appropriate for the production of break-free oils from partially de' gummed crude, samples of partially degummed oil containing 0.31% and 0.21% break were prepared by blending full crude containing 0.56% break with the correct proportions of a settled oil containing 0.13% break. Break-free oils were successfully prepared in accordance with the process of this invention using acetic anhydride as the degumming agent from extracted soybean oil containing 0.13%, 0.21%, 0.31% and full crude containing 0.56% break, as well as expeller soy oil and crude linseed oil. On the basis of these experiments as well as the examples set forth above, it is apparent that the process of this invention can be used to produce break-free oils from full crude vegetable oils and also from partially degummed vegetable oils.

A series of experiments were made to determine approximately the minimum amounts of acid anhydride required to degurn full crude soybean oil so as to obtain a break-free oil. Table I below is a tabulation of the results obtained by treating seven 500 gram samples of crude extracted soy oil heated to 60 C. with the various amounts of acetic anhydride indicated. In each instance the temperature of the oil sample was raised from 60 C. to C. in about 5 minutes after adding the acetic anhydride with stirring, after which time 3% of water (i. e. 15 grams) was added. The temperature of the mixture was held within the range of 60-75 C. for 15 minutes with vigorous stirring. Each of the samples was then centrifuged in 250 gram centrifuge bottles at 1800 R. P. M..for 15 minutes. The Gardner break was run on each sample of oil after the gums were separated.

8 Table I Percent of acetic anhydride: Results 0.4 Break-free. 0.3 Do. 0.2 Do, 0.1 Do. 0.08 Do. 0.06 Do. 0.04 Not break-free.

On the basis of the results tabulated in the foregoing table, it would appear that under the conditions employed 0.06% acetic anhydride would be sufficient to yield a break-free oil. However, accumulated experience indicated that 0.1% of the anhydride was about theminimum amount which would consistently give a breakfree oil. It was found that the amount of anhydride de' pends on the temperature and the amount of break in the crude oil. Thus, break-free oils Were obtained from full crude soy oil using 0.1% acetic anhydride at temperatures of 60 C. and 80 C., whereas 0.2% of the acetic anhydride was required at 40 C. Partially degummed soy oil containing 0.31% break gave break-free oil with 0.1% acetic anhydride at 60 C. but at 40 C. a minimum of 0.2% of the anhydride was required. Crude oil containing 0.21% break or less was not made break-free with less than 0.2% acetic anhydride at any temperature.

A series of experiments was made to determine whether or not the 1.5% of water based on the weight of the oil which is satisfactory in the known water degumming process, is also sufficient when acetic anhydride or other acid anhydride is used according to the present invention. In general, it is desirable to keep the amount of water to a minimum since increased amounts of water tend to increase the oil losses and also reduce the acetone insoluble content of the dried lecithin with all commercial specifications. It was found that crude oil containing 0.31% or more break can be made break-free according to this invention at temperatures from 40l00 C. using 1.5% water on the basis of the weight of the oil. Crude oil containing 0.21% break or less requires more degumming water, e. g. 3.0% water. Increased proportions of water in general reduce contact time requirements particularly at temperatures below 60 C.

Suitable tests showed that only very short contact times, in the order of a minute for example, are required for the acid anhydride and the oil before addition of degumming water, if this is the order of addition which is followed. Accordingly, when minimum amounts of the acid anhydride are to be used, the anhydride should be added to the oil prior to the addition of the water if the degumming process is to be carried out above 40 C. Break-free oils can be obtained at higher temperatures by adding the water before the anhydride provided that increased percentages of the acid anhydride are employed. There appears to be no particular advantage in adding the water to the oil ahead of the anhydride, whereas when the anhydride is added before the water the reagent-oil contact time can be very short and variations in the reagent-oil contact time appear to have little if any effect when the anhydride reagent is added prior to the addition of the degumming water.

It was further found that when the acid anhydride degumming reagent is added to the oil before the degurnming water the temperature of the oil is not critical within a wide range. That is, the reagent can either be added to the cold oil and then the oil heated to degumming temperature or the oil can be heated to degumming temperature before the anhydride is added. Apparently, the temperature at which the anhydride degumming reagent is added or is contacted with the oil is not particularly important except where the reagent is added after the degumming water has been first added, as discussed above.

Appropriate test determinations revealed that the degummin'g water-oil contact times vary with the temperature of and amount of'break in the crude oil. Thus, with a full break crude soy oil, using 3.0% degurnniin'g water, minutes contact time was required at C. whereas when 1.5% of degumming water was used, minutes contact time was required to produce break-free oil "at the same temperature. At a temperature of 60 ,C. or above, using 1.5 degumrning water, 5 minutes was about the minimum contact time that would yield a break-free oil, the other conditions remaining the same. Crude soy oil containing 0.21% break or less requires at least about 30 minutes contact time and at least about 3.0% degumming water to give abreak-free oil.

On the basis of a visual examination of the gums, it appears that increasing the water-oil contact time above the bare minimum up to a practical maximum will facilitate the removal of the gums by centrifuging. This observation was based on the appearance of the gums as they were deposited in the centrifuge bottle or the bowl. When only a bare minimum of contact time was allowed, the gum deposit was in definite. layers or stratified, indicating a non-uniform rate of settling. When the water oil contact times were increased, the gums deposited in a uniform layer.

It will be seen that the optimum or preferred operating conditions and procedure for degumming any particular vegetable oil with an acid anhydride in accordance with the present invention can be readily and easily deter mined by running a few simple tests. However, the foregoing disclosure and examples will provide a sufficiently accurate basis for determining the satisfactory operating conditions which may be followed so that prerun trials will not be essential.

In view of the foregoing disclosure, those skilled in the art will be able to practice the invention either according to the specific embodiments and directions set forth above, or according to other embodiments which will be obvious. Accordingly, all matter set forth above is intended to be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In the process of degumming a vegetable oil by treating the oil with water and thereafter separating the aqueous component from the oil, the improvement which comprises, treating the oil prior to separation of the aqueous component from the oil with a small amount of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride.

2. The method of refining a vegetable oil so as to degum the same and obtain an acid or Gardner break-free oil which comprises, intimately mixing with the vegetable oil degumming water and a minor quantity of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, and then separating the resulting aqueous phase from the oil phase.

3. The method of refining a vegetable oil so as to degum the same and obtain an acid or gardner break-free oil which comprises, mixing with the oil for a short period of time a minor amount of at least one acid anhydride selected from the group consisting of actic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, thereafter mixing the oil with degumming water for a relatively longer period, and separating the resulting aqueous phase from the break-free oil phase.

4. The method of refining a lecithin-bearing vegetable oil so as to degum the same and render it acid or Gardner break-free which comprises, mixing with the oil. for at least about one minute at least about 0.05 on the basis of the weight of the oil of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, then mixing with the oil at a temperature within the range of about 40-100 C. at least about 1.5% of water on the basis of the weight of the oil for a period of at least 5 minutes, and separating the resulting aqueous phase containing the gums from the break-free oil phase.

5. In the process of degumm'ing soybean oil by treating the oil with water and thereafter separating the aqueous component from the oil, the improvement which comprises treating the oil prior to separation of the aqueous component from the oil with a small amount of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl.

succinic acid anhydride and dimethyl succinic acid anhy-- dride.

6. The method of refining soybean oil so as to degum the same and obtain an acid or Gardner break-free oil which comprises, intimately mixing with the soybean oil degumming water and a minor quantity of at least one acid anhydride selected from the group consisting.

of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride.

7. The method of refining soybean oil so as to degum the same and obtain an acid or Gardner break-free oil which comprises, mixing with the oil for a short period of time a minor amount of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, thereafter mixing the oil with degumming water for a relatively longer period, and separating the resulting aqueous phase from the break-free oil phase.

8. The method of refining soybean oil so as to degum the'same and render it acid or Gardner break-free which comprises, mixing with the oil for at least about one minute at least about 0.05% on the basis of the weight of the oil of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, then mixing with the oil at a temperature within the range of about 40l00 C. at least about 1.5% of water on the basis of the weight of the oil for a period of at least 5 minutes, and separating the resulting aqueous phase containing the gums from the break-free oil phase.

9. The method of refining soybean oil so as to degum the same and render it acid or Gardner break-free which comprises, mixing with the oil for a period of at least about one minute at least about 0.05 on the basis of the weight of the oil of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride, then mixing with the oil for a period of at least 5 minutes and at a temperature in the range of about 60-85 C. at least about 1.5% of water based on the weight of the oil and separating the resulting aqueous phase containing the gums from the break-free oil phase.

10. In the process of degumming soybean oil by treat-- ing the oil with water and thereafter separating the aqueous component from the oil, the improvement which comprises treating the oil prior to separation of the aqueous 11 component from the oil with a small amount of acetic anhydride.

1 11. The method of refining soybean oil so as to degum the same and obtain an acid or Gardner break-free oil which comprises, intimately mixing with the soybean oil degumming water and a minor quantity of acetic anhydride.

12. The method of refining soybean oil so as to degum the same and obtain an acid or Gardner break-free oil which comprises, mixing with the oil for a short period of time a minor amount of acetic anhydride, thereafter mixing the oil with degumming water for a relatively longer period, and separating the resulting aqueous phase from the break-free oil phase.

13. The method of refining soybean oil so as to degum the same and render it acid or Gardner break-free which comprises, mixing with the oil for at least about one minute at least about 0.05% on the basis of the weight of the oil of acetic anhydride, then mixing with the oil at a temperature within the range of about 40-l00 C. at least about 1.5% of water on the basis of the weight of the oil for a period of at least 5 minutes, and separating the resulting aqueous phase containing the gums from the break-free oil phase.

14. The method of refining soybean oil so as to degum the same and render it acid or Gardner break-free which comprises, mixing with the oil for a period of at least about one minute at least about 0.05% on the basis of the weight of the oil of acetic anhydride, then mixing with the oil for a period of at least 5 minutes and at a temperature in the range of about 60-8S C. at least about 1.5 of water based on the weight of the oil and separating the resulting aqueous phase containing the gums from the break-free oil phase. 1

15. The method of refining a vegetable oil so as to degum the oil and produce acid or Gardner break-free edible vegetable oil which comprises, intimately contacting the vegetable oil with a minor quantity of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride and a quantity of degumming water, separating the resulting aqueous and oil phases, deodorizing the separated oil with steam at elevated jtemperature. and subatmospheric pressure, and recovering the distillate OOH": taining steam-distilled fatty material.

16. The method of refining soybean oil so as to degum the oil and produce acid or Gardner break-free edible soybean oil which comprises, intimately contacting soybean oil with a minor quantity of at least one acid anhydride selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, maleic anhydride, succinic anhydride, monomethyl succinic acid anhydride and dimethyl succinic acid anhydride and a quantity of degumming water, separating the resulting aqueous and oil phases, deodorizing the separated oil with steam at elevated temperature and subatmospheric pressure, and recovering the distillate containing steamdistilled fatty material.

17. The method of refining soybean oil so as to degum the oil and produce acid or Gardner break'free edible soybean oil and once-distilled fatty acids which comprises, mixing with the oil for at least about one minute at least about 0.05% on the basis of the weight of the oil of acetic anhydride, then mixing with the oil at a temperature within the range of about 40100 C. at least about 1.5% of water on the basis of the weight of the oil for a period of about five minutes, separating the resulting aqueous and oil phases, deodorizing the separated oil with steam at elevated temperature and reduced pressure, and recovering the distillate containing steam-distilled fatty material.

18. The method of claim 15 wherein the separated oil is bleached prior to deodorization.

19. The method of claim 16 wherein the separated oil is bleached prior to deodorization.

20. The method of claim 17 wherein the separated oil is bleached prior to deodorization.

References Cited in the file of this patent UNiTED STATES PATENTS 2,245,537 Thurman June 10, 1941 2,269,243 Baxter et a1 Ian. 6, 1942 2,410,926 Bush et al NOV. 12, 1946 2,567,404 Ross Sept. 11, 1951 2,666,074 Sadler Ian. 12, 1954 

1. IN THE PROCESS OF DEGUMMING A VEGETABLE OIL BY TREATING THE OIL WITH WATER AND THEREAFTER SEPARATING THE AQUEOUS COMPONENT FROM THE OIL, THE IMPROVEMENT WHICH COMPRISES, TREATING THE OIL PRIOR TO SEPARATION OF THE AQUEOUS COMPONENT FROM THE OIL WITH A SMALL AMOUNT OF AT LEAST ONE ACID ANHYDRIDE SELECTED FROM THE GROUP CONSISTING OF ACETIC ANHYDRIDE, PROPIONIC ANHYDRIDE, BUTYRIC ANHYDRIDE, MALEIC ANHYDRIDE, SUCCINIC ANHYDRIDE, MONOMETHYL SUCCINIC ACID ANHYDRIDE AND DIMETHYL SUCCCINIC ACID ANHYDRIDE. 